Working with Human Pathogens and Toxins

“Human pathogens and toxins pose a small but significant risk to human health and safety, either through accidental or deliberate release. Accidental release can result from inadequate controls on activities such as possession, use, transfer or disposal. A deliberate release could be possible if there are inadequate security measures in place. To address these concerns, the Public Health Agency of Canada (PHAC) established a national safety and security program to protect the health and safety of the public against risks posed by human pathogens.”

Chapter 2 of the Canadian Biosafety Handbook provides important information that lab users need to know. Some microorganisms (viruses, bacteria, fungi, etc.) are species specific, selectively infecting and causing disease in a limited number of, or only one, host species. Unrelated and distantly related species may not be similarly affected by the same infectious microorganism due to differences in physiology, metabolism, biochemistry, etc. In general, the risk to a laboratory technician working with a virus that only infects and causes disease in rodents is lower than the risk to a laboratory technician working with tissues and cells from humans or other primates. If the human material contains a viable pathogen, it will likely be a human pathogen, with the potential to infect and cause disease in another human.

Although a single mode of transmission may predominate, disease-causing microorganisms can be spread or transmitted:

from one host to the next;

directly or indirectly;

by aerosol generation and inhalation;

via ingestion of contaminated food and water;

through skin and mucous membrane contact with contaminated surfaces;

through contact contamination of an open wound or lesion;

via autoinoculation through a cut, laceration or puncture with a contaminated instrument.

Human Bloodborne Pathogens

Human blood, a potential source of pathogenic microorganisms, presents a risk to workers. Although the hepatitis B virus (HBV) and the human immunodeficiency virus (HIV) are often cited as examples, a “bloodborne pathogen” is any pathogenic microorganism that is present in human blood or other potentially infectious materials that can infect and cause disease in persons who are exposed to blood containing the pathogen.

The biosafety requirements identified for research laboratories may not always be applicable to all workplace settings where workers handle or are exposed to human blood, body fluids or other materials potentially containing biological materials.

Universal Blood and Body Fluid Precautions

Between 1982 and 1988, the Centers for Disease Control (Atlanta, Georgia) published a series of recommendations and precautions for the protection of healthcare workers (physicians, nurses, phlebotomists, dentists, laboratory workers, etc.) who have, or are likely to have, contact with human blood and certain body fluids and may be at risk of exposure to bloodborne pathogens such as hepatitis B virus (HBV) and human immunodeficiency virus (HIV). These recommendations became known as the “Universal Blood and Body Fluid Precautions” or simply, the “Universal Precautions”.

The possibility of undiagnosed infection combined with the increasing prevalence of HBV and HIV led the Center for Disease Control to recommend that blood and certain other body fluids from all humans be considered potentially infectious and that precautions be taken to minimize the risk of exposure. This approach (the “Universal Precautions”), is a method of infection control intended to prevent parenteral, mucous membrane, and non-intact skin exposure of workers to bloodborne pathogens. All human blood, certain human body fluids, and other materials are considered potentially infectious for hepatitis B virus (HBV), human immunodeficiency virus (HIV), and other bloodborne pathogens. Precautions must be consistently undertaken.

Universal blood and body fluid precautions apply to:

blood

body fluids containing visible blood

semen

vaginal secretions

cerebrospinal fluid

synovial fluid

pleural fluid

peritoneal fluid

pericardial fluid

amniotic fluid.

Universal precautions generally do not apply to faeces, breast milk, nasal secretions, sputum and saliva, sweat, tears, urine or vomitus unless they contain visible blood. Although these biological materials are not implicated in the transmission of bloodborne pathogens, it is prudent to minimize non-intact skin and mucous membrane contact with these biological materials. A Biosafety Permit is required to work with these materials.

Hepatitis B immunization is required as an adjunct to universal precautions for workers who have occupational exposure to human blood or other potentially infectious materials. This immunization is provided free of charge to employees at risk by the EHS’ Occupational Health Nurse.

General Precautions

All staff, students, and visitors should routinely use appropriate barrier precautions to prevent skin and mucous membrane exposure when contact with human blood or other body fluids is anticipated.

Gloves should be worn when touching blood and body fluids, mucous membranes or non-intact skin, handling items or surfaces soiled with blood or body fluids, and for performing venipuncture and other vascular access procedures. If a glove is torn or damaged during use, it should be removed and a new glove used as promptly as safety permits. Disposable gloves should not be washed or disinfected for reuse. Washing with surfactants may enhance penetration of liquids through undetected holes in the glove and disinfecting agents may cause deterioration of the glove material.

Protective eyewear, appropriate respiratory protection or face shields should be worn during procedures that are likely to generate droplets of blood or other body fluids to prevent exposure of mucous membranes of the mouth, nose and eyes.

Gowns or aprons should be worn during procedures that are likely to generate splashes of blood or other body fluids. Protective clothing should be removed before leaving the area.

Hands and other skin surfaces should be washed immediately and thoroughly if contaminated with blood or other body fluids. Hands should be washed immediately after gloves are removed since no barrier is 100% effective.

Staff, students, and visitors should take precautions to prevent injuries caused by needles, scalpels, and other sharp instruments or devices during procedures, when cleaning used instruments, during disposal of used needles, and when handling sharp instruments after procedures. Needles and syringes should be used only in those situations when there is no alternative. To prevent needlestick injuries, needles should not be recapped, purposely bent or broken by hand, removed from disposable syringes, or otherwise manipulated by hand. If recapping is not avoidable, proper procedures must be established (single hand recapping or using tools to recap) and documented. After they are used, disposable syringes and needles, scalpel blades, and other sharp items should be placed in puncture-resistant containers for disposal. The puncture-resistant container should be located as close to the use area as practical. Contaminated reusable pointed and sharp objects such as large bore needles and scalpels should be placed in a puncture resistant container for transport to the reprocessing area.

Staff, students, and visitors who have exudative lesions, weeping dermatitis, cuts, open wounds or other breaks in the skin should either refrain from all direct contact with blood and other body fluids until the condition resolves, or else utilise protective barriers to reduce the risk of exposure.

Pregnant workers should be especially familiar with and strictly adhere to precautions to minimize the risk of perinatal transmission of bloodborne pathogens.

Additional Precautions for Clinical Laboratories

All blood and body fluid specimens should be in a well-constructed container with a secure lid to prevent leakage during transport.

Gloves should be worn by all persons processing blood and body fluid specimens. Gloves should be removed and replaced and hands should be washed upon completion of specimen processing since no barrier is 100% effective.

Masks and protective eyewear or a face shield should be worn if there is the potential for mucous membrane contact with blood or body fluids.

A biological safety cabinet is not necessary for routine procedures such as histologic and pathologic studies or microbiological culturing. However, biological safety cabinets should be used whenever procedures involve activities that have a high potential for generating aerosol droplets (blending, sonicating, vigorous mixing, etc.).

Mechanical pipetting devices should be used for manipulating all liquids in the laboratory.

Laboratory work surfaces should be decontaminated with an appropriate chemical germicide after a spill of blood or other body fluids and when work activities are completed.

Hands should be washed after completing laboratory activities and protective clothing should be removed before leaving the laboratory area.

Equipment and instruments should be decontaminated and cleaned before being repaired in the laboratory or transported to the manufacturer or repair shop.

Contaminated materials must be decontaminated before processing for reuse. Disposable contaminated wastes must be collected in the appropriate containers.

Additional Precautions for Autopsies or Morticians’ Services

Instruments and surfaces contaminated during postmortem procedures should be decontaminated with an appropriate chemical germicide. Gloves should be worn during the cleaning and decontaminating procedure.